Help with formula to find interest rate

Hello -

I am trying to solve for the implied interest rate.

So in this example, I have the option to pay someone $2,000 today, or $23.33 every month for 10 years (120 equal payments) for a total of $2,800.

I can't figure out which formula(s) to use to find what the implied interest payment would be in this situation so I can decide if it makes sense to pay now or over time.

What formula(s) would I use?

Thanks.